message: Zip file contains illegal contents

I am trying to upload two zip files (created with Articulate).  I have previously uploaded these types of files with no problem.  These file uploads produce the message, 

Zip file contains illegal contents.  

I looked at this blog to explore why: https://blogs.connectusers.com/connectsupport/content-fails-to-upload-to-connect-with-error-message-illegal-content/

Then I unzipped the file to see if any of the blocked executable extensions might be present.  I found none.  

I need helpl figuring what's wrong with these files.